Nasri scored two penalties in extra-time as Arsenal knocked arch-rivals Tottenham out of the competition.

However, Redknapp believes Nasri threw himself to the ground under Sebastien Bassong's challenge to win Arsenal's 92nd-minute spot-kick, from which they took the lead at 2-1.

Redknapp said: "I thought the first one was harsh. He fell over. Really I think he dived for the first penalty."

Arsenal manager Arsene Wenger had to watch the match from the stands, having accepted a misconduct charge and fine by the Football Association following his actions at the end of their 1-1 draw with Sunderland at the weekend.

"We played well in the first half, but were only one goal in front after Tottenham came back," he said. "We were for a few minutes in danger, but afterwards took over again, but could not score in the final 20 minutes.

"Then we got these two penalties, which were penalties, and that was the turning point of the game."

Wenger also revealed that Nasri had previously resisted taking penalties after fouls on himself.

"He had a superstition to think that when a penalty is made on you not to take it," Wenger said.

"But I tried to prove to him that that's solely based on fear. He realises now that it was a bad superstition."